"Stand up if you want to, but keep close to the wall," ordered Dad, himself rising to his feet.
One by one the boys got up, Professor Zepplin following the example of the guide. They had to shout in speaking in order to make themselves heard above the bombardment, the roaring of the river and the cataract over their heads.
"What is going on up there?" shouted Tad.
"Mountain falling in!"
"I knew it! I knew it!" yelled Chunky. "I knew something would fall down as soon as I got here."
No one laughed. The situation was too serious for laughter.
"Is it a land or a rock slide?" questioned Tad further.
"Both," shouted Nance. "Mostly boulders."
The rain has loosened them and they are raining down on us. We're lucky we had this shelf to get under."
"From the present outlook I am afraid the shelf isn't going to protect us much longer," said Tad.